The permanent alteration of the color of keratinous fibers, in particular human hair, by the application of hair dyes is well known. Oxidative hair dye precursors, i.e., developers (also called primary intermediates) and couplers diffuse into the hair through the cuticle and into the cortex. The precursors combine in the presence of an oxidizing agent, such as hydrogen peroxide, to form larger-sized dye molecules that result in a visual color of the hair (“end hair color”). Different combinations of developers and couplers produce different shades of hair color when combined with the oxidizing agent. The end hair color is not easily predicted given the complex chemical process that occurs to achieve an end hair color.
Permanent hair colorant formulations should produce end hair colors that are stable for at least 4 to 6 weeks. Additionally, the end hair color should exhibit good washfastness, good lightfastness, fastness to rubbing, as well as sufficient resistance with respect to perspiration. Preferably, it should be possible to produce a broad palette of different color shades by combining suitable developers and couplers.
An approach that has been successfully used over many years is the use of p-phenylenediame and toluene-2,5-diamine as developers to deliver the majority of hair colorants in the market today. A current trend is to reduce the amount of the p-phenylenediamine and/or toluene-2,5-diamine by using other analogues of p-phenylenediamine, but not all of them can deliver the desired color and are compatible with p-phenylenediamine/toluene-2,5-diamine Additionally, owing to the unique color performance of p-phenylenediamine and toluene-2,5-diamine, there are cases where blending is necessary to achieve desired color performance.
Canadian patent application number CA2567189 discusses the combination of 2-methoxymethyl-1,4-diaminobenzene with a number of other primary and coupler materials, but not explicitly the combination with other 1,4-diamines. By combining 2-methoxymethyl-1,4-diaminobenzene with 1,4-diamines selected from the group consisting of p-phenylenediamine and toluene-2,5-diamine, it is possible to blend developers together to deliver desired colorations whilst enabling concentrations of specific types of 1,4-diamines to be reduced. This creates potential for full color benefit delivery with preferential selection of hair colorant starting materials.
There remains an ongoing need for additional hair colorant compositions that can provide desirable shades that meet consumer preferences, particularly when used with various oxidant systems, i.e., ammonium carbonate, hydrogen peroxide, and, optionally, a radical scavenger and/or chelant.